Rheostat.



No. 745,077. PATENTED NOV. 24, 1903.

W. A. SHERLOCK.

RHEOSTAT.

APPLICATION FLBD JAN. 16, 1903.

H0 MODEL.

INVENTOR we mums Pntws c UNITED STATES Patented November 24, 1903.

WALTER A. SHERLOCK, OF SAN FRANCISCO, CALFORNIA.

RHEOSTAT.

SPECXFICATION forming part of Letters Patent No. 745,077, dated November 24, 1903.

Application filed January 16, 1903. Serial No. H9308. {No modell' To all whom it 717/601/ concern.:

Be it known that I, WALTER A. SHERLOCK, a citizen of the United States, and a resident of San Francisco, in the county of San Francisco and State of California, have invented a new and Improved Rheostat, of which the following is a full, clear,and exact description.

My invention relates torheostats, my more particular object being to produce a neat, compact, and efficient form of instrument capable of general use and especially suitable forcutting down the current of ordinary service-Wires by merely tapping into the wires.

Reference is to be had to the accompanying drawings,forining a part of this specification, in which similar characters of reference indicate corresponding parts in all the figures.

Figurel is a central section through the rheostat proper. Fig. 2 is a perspective view showing the rheostat in use and also showing the electrical connections; and Fig. 3 is a diagram showing the electrical connections, the rheostat being in use.

A corrugated metallic tube 1, having substantially the form of a longitudinal cylinder, is provided at its respective ends with porcelain caps 2 3, these caps being fitted with metallic contacts 4 5, preferably of brass.

Disposed Within the tube 1 are tillings 6 7 of insulating material, preferably plaster-ofparis. These fillings serve to hold the tubes 3 9, of glass,firmly in position. Platinum Wires 10 1l are disposedin pairs and are sealed into the tubes 8 9, the wires 10 being longer than the Wires 11, and therefore exposing a greater surface.

Into the central portion of the cylindrical tube 1 is solidly packed a semiconducting composition 12, which acts as a resistance to the passage of the electric current, and so forms an essential part of my invention. The substance and chief factors of this composition are preferably eighty per cent. of a mixture of powdered carbon and peroxid of iron invaryingproportions,as ten is to seventy,and conversely, depending upon the ohmic resistancerequired. Theremainingtwentypercent. of the composition is composed of plaster-ofparis or other such clay-like substance acting as a filler and serving to secure the ren sistance in compact solid form. This material allows the tiow of a quantity of current proportionate to the area of the wire-surface eX- posed thereto.

r Phe platinum Wires lO 11 are connected with the Wires 13 14, which may be made of copper or other conducting material, and branch therefrom at the junctions 15 16, as indicated in Fig. 1. An ordinary incandescent-lamp socket 17 is provided with the usual thumbpiece 18 for opening and closing the circuit, and it is also provided with the usual inner contact 19 and outer contact 20, this outer Contact being threaded and otherwise adapted to receive the cylindrical member 1. The inner and outer contacts are connected, respectively, with the Wires 21 22. The other end of the Wire 22 may be connected with any desired apparatus-such, for instance, as an electrolytic bath. A third wire 23 is also connected with the bath. The two Wires 21 23 are connected, respectively, with the inner contact 24 and the outer contact 25 of the tapplug. The tap-plug may be of any desired pattern;but I preferably use one made by binding together the base of an incandescent lamp and a porcelain insulator-knob.

Referring to Figs. 1 and 3, it will be observed that the porcelain insulator-knob 2G is connected with the outer terminal 25, the inner terminal 24 being separated from the outer terminal by means of the insulation 27, as is usual in incandescent lamps.

My invention is used as follows: Suppose that it is desired to tap into the service-main for the purpose of using a Weak current in connection with the process of electroplating. The tap-plug (shown at the upper portion of Fig. 1) is screwed into the ordinary socketfixture used for tapping the mains. The rheostat (shown in Fig. 1) is also inserted in the lamp-socket 17. The wires 22 23 are connected with the terminals of the electrolytic bath, and the current is turned on by means of the thumb-piece 18 in the usual manner. The current follows the course indicated in Fig. 3 and passes from the tube 1 through the semiconducting material to the platinum Wires 11 and thence to the inner contact 5. If, however, a more powerful current is requiredsay for stripping, acid-coloring, or rose-coloring, or for any other purpose requiring a stronger current--the flow of the current is IOC stopped bymeans of the thumb-piece 18 and the rheostat is taken out and turned around so that the end provided with the contact 4 is inserted in the socket. The current will now pass from the cylinder l through the semiconducting material and platinum wires 10 to the wire 13 and the inner contact t. l have found that this type ot' rheostat so handles the current that the energy thereof is choked or throttled, asit were, and comparatively little of the energy is used in heating the semiconducting` material.

Having thus described my invention, l claim as new and desire to secure by Letters Patent l. Arheostat,comprisingarheostatic meinber proper provided with inner and outer coutacts and with a semicondnoting,` material disposed in the path of the current as between said contacts, and a separate socket likewise provided with inner and outer contacts for engaging the respective inner and outer contacts of said rheostatic member proper.

2. A rheostat, comprising a metallic hollow member serving as a receptacle and also as a contact of one sign, separate groups of conducting members mounted within said hollow member and insulated therefrom and from each other, contacts of another sign connected with said conducting,r members and insulated from said hollow member, and a semiconducting,` material engaging said conducting members and also engaging said hollow metallic member for the purpose of offering` a resistance to the passage of the current.

3. A rheostat, comprising a metallic hollow member serving as a receptacle and also as a contact, conducting members disposed within said metallic hollow member and provided with surfaces of different area, said conducting members being` insulated from said hollow member and 'from each other, a semiconducting,` material disposed in cont-act with said hollow member and with said surfaces of different area, a semiconducting material disposed within said hollow member and in con- 5. A rlieostat, comprising a substantially cylindrical tube made ot conducting,Y material and capable of use as a contact, resistance mechanism mounted within said tube, and separate contacts disposed at each end of said tube and insulated from each other, said separate contacts being.Y connected with said resistance mechanism.

G. ln a rheostat, the combination of a me tallic hollow member provided with a threaded surface and capable of use both as a rcceptacle and as a contact, conducting members mounted within said hollow member and insulated therefrom, conta ts connected with said conducting members, and a semiconducting.;` material in actual contact with said hollow member and said cond noting,` members.

7. in a rheostat, the combination of a metallic tube provided with a contact-surface, contacts connected with said tube and insulated therefrom and `trom each other, and a semiconducting material disposed in electrical commui'iication with said contacts and with said tube.

8. in rheostat, the combination of a me tallic tube provided with a coiitact-surlacc, contacts connected with said tube and insulated therefrom, and a semiconducting material engaging` said tube and said contacts.

ln testimony whereof l have signed my ame to this specification in the presence ol two subscribing witnesses.

WALTER A. SHERLOCK.

.Vitnesses:

HARRY J. HoLLANDnn, G. W. KUEHN. 

